Mechanism and circuitry for high voltage switching



Feb. 23, 1965 E. L. LUEHRING 3,171,004

uscnmsu mo cmcuxm FOR man vomcs su'rcamc Filed July 18. 1961 3 Shoots-Shoot 1 INVENTOR. ELMER L. LUEHRING ATTORNEY Feb. 23, 1965 E. LUEHRING 3,171,004

MECHANISM AND CIRCUITRY FOR HIGH VOLTAGE SWITCHING Filed July 18, 1961 3 Sheets-Sheet 2 LATCH (44,42) FIG-2 MA 452 33(25) PATH 6mm?) AsQw-n fi H J Lowm IMPEDANCE PATH l2 -M |3 2 L HI. CUR. LOW CUR. SEQUENCE A DA LATCH B LATCH B As FULL CLOSED OPEN OPEN OPENING OPENS OPEN OPEN OPENS OPENS OPEN OPEN II I N u I n CLOSING mmvron. ELMER LUEHRING ATTOR N EY Feb. 23, 1965 E. L. LUEH RING MECHANISM AND CIRCUITRY FOR HIGH VOLTAGE SIITCHING Filed July 18. 1961 3 Sheets-Sheet 3 r" 5 g I I i L l% L2 M BY PASS BY PASS 25 M A OPENING SEQUENCE I 2 3 4 WITH HIGH CURRENT OPENING SEQUENCE I 2 3 WITH LOW CURRENT OR AITERNATIVE ARRCT.

(NOT sHowN) 2 NONE FIG-4 INVENTOR.

ELMER L. LUEHRING ATTORNEY United States Patent F 3,171,004 MECHANISM AND CIRCUITRY FOR HIGH VOLTAGE SWITCHING Elmer L. Luehring, Cleveland, Ohio, assignor to Joslyn Mfg. and Supply Co., Chicago, IlL, a corporation of Illinois Filed July 18, 1961, Ser. No. 124,899 4 Claims. (Cl. 200--146) This invention relates to a high voltage switch and has particular significance in connection with means for reducing the cost of associate equipment.

High voltage power line switching apparatus of well known type comprises, for example for each phase, main air break contacts and an associate enclosed-against-ambient (e.g., vacuum) load interrupter device with interlocking, usually mechanical, such that the main contacts will open first, while the circuit is kept closed through the interrupter device, and the interrupters will open later so that there is no destructive arcing, although numerous modifications of such sequence are well known, see for example US. Pat. 2,955,181, issued October 4, 1960, on an application filed by E. L. Luehring, and assigned to the assignee of the present invention.

By now the capabilities of vacuum switches have been demonstrated in hundreds of applications on electric utility systems. Unfortunately it has become commonplace for purchasing engineers to specify the voltage rating of a given load interrupter by simply stipulating voltage rating of the system on which the interrupter is to be installed.

It is an object of the present invention to obviate the spending of hundreds of thousands of dollars for load interrupter equipment whose voltage capability is far in excess of voltage requirements.

The present invention has its basis in part in recognition of the fact that recovery voltage which an inter-. rupter must withstand is only vaguely related to system operating voltage, and that significant economies can be realized if voltage ratings of interrupters are matched to anticipate recovery voltage conditions as predetermined by circuitry regardless of the voltage rating of the lines on which they are to be installed.

Other objects and advantages may become apparent and the invention may be better understood from consideration of the following description taken in connection with the accompanying drawing, in which:

FIG. 1 is a side view portion of a main switch shown part open and showing a vacuum interrupter with the vacuum interrupter contacts in closed position and with actuator mechanism provided with a latch according to one embodiment of the invention;

FIG. 2 is a schematic diagram with an accompanying table to show typical operating sequence for apparatus as in FIG. 1;

FIG. 3 is a one line simplified electrical circuit diagram of power system interconnections for the purpose of describing operation both according to the prior art and according to the invention; and

FIG. 4 shows a modification.

In FIG. 1 hereof (as in FIG. 2 of the above mentioned Pat. 2,955,181) a fixed insulator cooperates with a movable insulator (not shown). Insulator 10 carries a contact support plate 11, which has a main switch contact 12 arranged for cooperation with a main switch 3,171,004 Patented Feb. 23, 1965 blade 13 which is controlled by a switch arm 14 (and the movable insulator), the arrangement being such that the main switch arm 14 (on closing) will first swing downward in an arc and thereafter the blade 13 will slide horizontally into a slot in contact 12. On reverse action (for opening) the arm is first moved horizontally to disengage the blade from the slot after which the .arm 14 is swung to a vertical position. As in the patent, support plate 11 carries a torsion rod biased arcing horn 16 cooperable with an arc horn 17 which also serves as an actuator driver sleeve for operating vacuum interrupter mechanism, as hereafter described, so that one or more vacuum interrupter assemblies 20 may be operable from movement of an actuator arm 21 as it is forced to the left in FIG. 1 (to open the bottles during one portion of the sequence but only under certain conditions as hereafter described) or as it moves back down by spring force or gravity (to close the vacuum bottle contacts during another portion of the main switch opening sequence).

As explained in the patent, each interrupter assembly may have an outer shell 22 of insulating material with flange holes provided for receiving bolts 23 for fastening together like units and each may contain a glass 24 enclosed vacuum interrupter comprising coaxial contact rods 25 extending into the glass envelope, one from each of two end caps, and engaging the other rod within the envelope during interrupter closure.

One of more operating rods 27 operate cross bars 28, one for-each unit, while all the units are actuated through rods 27 by an operating plate 29 which in turn is op-v erated vertically by an eye bolt 30 secured to a slotted connecting link 32 cooperating with a secondary toggle lever 33. The toggle mechanism is arranged to be actuated by a spring 34 attached to an actuator crank 35 con-. nected for rotation with the actuator arm 21.

As explained in the patent there may be a torsion bar mounted actuator arm stop 37 to limit downwardtravel of actuator arm 21 and these parts (21, 37) can serve to short out the circuit of the vacuum bottles for certain steps of the operating sequence.

In accordance with the illustrated embodiment of the present invention, a low current lock-in or latch mechanism comprises an iron solenoid core 40, a magnetic material frame (return path) 41, a pivoted armature portion 42 which is biased open by a spring 43, and a solenoid coil 44, with the armature normally (when coil is deenergized) engaging one of the toggle members (such as 33) to keep the interrupters closed. The winding 44 about core 40 may be a one or two layer strap winding and as shown is in the circuit of the line L1 (when the parts are engaged) and through interconnections such as 45, 46, 47, with the series circuit of the vacuum interrupters.

As indicated in FIGS. 1 and 2, when opening action is initiated, the main switch arm is first horizontally withdrawn to disengage blade 13 from main contact 12 but this movement first closes arc horn 17 upon 16. Next the arm 14 and its blade 13 swing upward in an arc causing the are horn driving sleeve 17 to engage actuator arm 21, and then an electrical circuit may be traced from an assumed outside line shown diagrammatically at L1 to arm 14, blade 13, sleeve 17, arm 21, crank 35, and to the strap 45, and then through the solenoid coil 44, through lead 46, top interrupterunit contacts 25, top interrupter bottom strap 47, and then through similar series leads to successive interrupters (if any) therebeneath and finally out to the other side of the line designated as L2 (in circuit with 37 and 16).

With continued upward arcuate movement of main blade 14 the arc horn 17 carries the actuator arm 21 upward extending and moving the spring 34 until the spring center passes by lever 33 tending to pull up on 33 but moving it only if armature 42 does not restrain lever 33. With proper spring loading and mechanical and electrical design the armature extension will not pull out of the way of toggle operation until some low value of current (for example, 50 amps and below) is exceeded. Since the center of rotation of crank is properly eccentric with respect to the linkage mechanism, tension built up in the spring 34 (as soon as the spring passes link 33) causes parts 30, 29, 27, 28 to quickly spring up so that the circuit is broken through the various vacuum interrupters (providing the requisite high current exists).

Ultimately, with continued upward arcuate movement of arm 14, the driving sleeve 17 leaves the end of actuator arm 21. This breaks the circuit through the solenoid coil 44 so that under spring force armature 42 extension tends to again engage the slot as contacts 25 close when the arm 21 falls back down due to its own weight (and is pulled down by spring 34) so as to rcclose the contacts 25 and relax the spring, although the above described sequences are not necessary for operation in accordance with the present invention and it may be that it would be desired, rather, to have the vacuum contacts not reclose until some time during the sequence of closing of the main switch or its arc horns (17, 16).

Referring now to FIG. 3, I have shown two high voltage sources represented schematically at 61 and 62 and arranged to selectively or simultaneously supply a load indicated at 63 through usual equipment including lines (which may have distributed inductance 64 and capacitance to ground 65), oil circuit breakers of which 66 is shown open and 67 is shown closed, and isolating switches 71 and 72.

Assuming 67 and 72 closed, it circuit breaker 66 is open and switch 71 is closed and then caused to open, the recovery voltage across 71 (i.e., the voltage tending to re-establish the circuit) will be high, perhaps even exceeding the system line to ground voltage. The current through switch 71, however, is very low and it can be interrupted in air (by are horns) without the use of vacuum interrupter equipment.

If, on the other hand, all switches and breakers are closed, loop currents are flowing, and if the line connected through switch 72 is opened, the recovery voltage across 72 will be a small part of the line to ground voltage but the current will be high, possibly exceeding the load current through 63 (depending on phase angle and terminal voltage of generators). Such high currents can not safely be opened in air (through arc horns) and use of the vacuum interrupter is advantageous, but the interrupter on 72 does not have to be able to open a high voltage and can be sized to handle only the anticipated small recovery voltage even though it would not be able to withstand the recovery voltage discussed in connection with switch 71 (without application of the present invention).

Thus it is part of my invention or discovery that one so called bottle per phase may suffice on a 115 kv. line because this is ample for loop currents when it is made impossible to open charging currents except through air arc horns. Therefore in accordance with the invention I hold closed the vacuum bottle contacts unless there is present a predetermined minimum value of current (with might be 50 amps or might in some cases be 15 amps or /2 amp) whereby the vacuum interrupter is prevented from operating whenever there would be a substantial voltage difference after its operating (when there is present only a small charging current, of, for example or 10 amps). While a solenoid released latch was shown, it should be understood that other means might be used for interlocking and it would not even have to be automatic. Thus reliance might be placed instead upon an ammeter plus the brain of a human operator.

FIG. 4 shows modifications both in main electrical circuitry (the load interrupter contacts 25 being in series, rather than in parallel, but still in circuit with, the main contacts M) and in mechanical lock-in arrangement. Like parts are like identified as in FIGS. 1 or 2 but the arc horns A are shown dashed (because arc horns may or may not be used), and the bottle is also shown dashed because the load interrupter device to be protected may or may not be enclosed against ambient.

In FIG. 4 the lever 33 operates through a modified form of slotted link 32a which serves to open the load interrupter contacts 25 whenever high current exists in solenoid winding 44 so as to overcome the force of a tension spring 80. But when low current exists spring pulls a pin 30p to the left so that vertical elongation of the slots in 32a renders 33 ineffective to open the contacts 25. Many modifications are possible and as shown by the table of FIG. 4 instead of holding in the interrupter contacts 25 (when a predetermined current is not exceeded) the same result could be accomplished by holding in a by pass switch which often is already provided for prior art purposes not connected with the pres ent invention and relating to contact closing sequence.

While I have illustrated and described a particular embodiment, various modifications may obviously be made without departing from the true spirit and scope of the invention which is intended to be defined only by the appended claims taken with all reasonable equivalents.

I claim:

1. In a high voltage switch, the combination of a first device comprising load interrupter contacts, a second device having contacts connected to said interrupter contacts whereby to serve as a bypass for the first mentioned device, a third device which comprises the main contacts of the switch, with the parallel circuit of load interrupter and by pass being in series with the main contacts and with the parts mechanically connected and arranged so that during switch opening sequence the load interrupter is normally operable for opening before the main contacts open, and means for holding at least one of said first and second devices closed when the value of current through one of the devices is smaller than a predetermined value.

2. In a high voltage switch, the combination as in claim 1 further characterized by a fourth device which comprises air are horns electrically in parallel with the main contacts and mechanically arranged to open sequentially after the main contacts.

3. In a high voltage switch mechanism, the combination of a first set of contacts which are the main contacts of the switch, a second set of contacts which are air are horns electrically in parallel with the main contacts and mechanically arranged to open after the main contacts open during the switch opening sequence, a third and a fourth set of contacts with the third and fourth sets electrically in series with each other and with such series circuit in parallel with the parallel circuit of the first and second set, said switch being mechanically arranged so that the third set opens after the second set during opening sequence while the fourth set opens after the first set during opening but closes sequently thereafter during the opening sequence, and a fifth set of contacts which is a load interrupter device electrically in parallel with the fourth set of contacts and mechanically arranged to open after the second set and after the fourth set and before the third set but only when there exists a predetermined minimum current value through the fifth set, said fifth set of contacts remaining closed all during the opening sequence when lower values of current pass therethrough.

4. In a high voltage switch, the combination of claim 3 further characterized by lever means connected to one of the contacts of the fifth set, said lever means being initially actuated by opening of the main contacts, and means comprising a solenoid operated latch mechanism References Cited in the file of this patent UNITED STATES PATENTS Rawlins Feb. 25, 1936 Thommen Feb. 4, 1958 

1. IN A HIGH VOLTAGE SWITCH, THE COMBINATION OF A FIRST DEVICE COMPRISING LOAD INTERRUPTER CONTACTS, A SECOND DEVICE HAVING CONTACTS CONNECTED TO SAID INTERRUPTER CONTACTS WHEREBY TO SERVE AS A BYPASS FOR THE FIRST MENTIONED DEVICE, A THIRD DEVICE WHICH COMPRISES THE MAIN CONTACTS OF THE SWITCH, WITH THE PARALLEL CIRCUIT OF LOAD INTERRUPTER AND BY PASS BEING IN SEREIS WITH THE MAIN CONTACTS AND WITH THE PARTS MECHANICALLY CONNECTED AND ARRANGED SO THAT DURING SWITCH OPENING SEQUENCE THE LOAD INTERRUPTER IS NORMALLY OPERABLE FOR OPENING BEFORE THE MAIN CONTACTS OPEN, AND MEANS FOR HOLDING AT LEAST ONE OF SAID FIRST AND SECOND DEVICES CLOSED WHEN THE VALUE OF CURRENT THROUGH ONE OF THE DEVICES IS SMALLER THAN A PREDETERMINED VALUE. 